It's like public storage where you have to sift through everyone else's crap to get to yours, every item is stored in a bulk cargo box and only one customer gets to store their stuff at a time.
If you're interested in db internals, here's a few algorithms that MySQL uses. Note this doesn't cover InnoDB which performs far better under high concurrency loads and offers row level locking, clustered indexes, an excellent caching algorithm, foreign key constraints with cascade, etc..etc...
#get the file, decode, etc.
Thanks, I'll check out the MySQL thing, but I'm not actually intending to build my own database.